The present invention is generally relates to a surface-mount device ("SMD") which encapsulates a semiconductor chip. More particularly, the present invention relates to such a SMD having at least one active RF component or an integrated RF circuit with RF terminal locations contacted by bond wires within an interior of a housing to interconnects of a system carrier. The system carrier has a ground platform on which the semiconductor chip is mounted, the ground platform forming outer terminals.
SMD's with plastic housings are generally known for semiconductor chips with a discrete semiconductor component or an integrated circuit (IC). The chip is glued or eutectic bonded to a metallic system carrier, what is referred to as a leadframe, namely on a central part or island thereof given standard components or, respectively, standard ICs, and wires are bonded to the chip. The chip is also completely enveloped with a plastic molding compound in an injection molding process such that only the ends of the system carrier serving as outer terminals project therefrom.
Active high-frequency components such as, for example, silicon bipolar transistors, silicon ICs, GaAs MMICs (monolithic microwave circuits) are usually mounted in a plastic SMD housing for cost reasons. As the frequency increases, the properties of the RF components are negatively influenced to a greater degree by the housing. In particular, the new module radio telephone fields given frequencies of 1.8 GHz and given frequencies of 2.4 GHz and higher in future require cost-beneficial plastic housings having good RF properties for the active RF components in transmitters and receivers. In transmitter units, the thermal conductivity of the leadframe also plays a part since high dissipated powers must be eliminated in some applications.
Until now, RF housings were constructed as small as possible in order to minimize the mass inductances. Given that frequencies are becoming higher and given the introduction of SMD technology, problems have been encountered in further miniaturization of the housing since relatively large chips must also be packaged. As an attempt to then improve the ground, a plurality of pins and pins adjacent the RF terminals (housing terminals) have been applied to ground. Although this configuration improves the grounding conditions and provides additional RF shielding, the characteristic impedance of that arrangement becomes so high because of the usually great spacings between the pins, however, that a great transformation occurs. Moreover, the conventional ground-conducting terminals are just as narrow as the RF terminal, so that a true, low-impedance waveguide does not arise.